By default, SCons removes all built targets when invoked
with the -c option to clean a source tree
of built targets.
Sometimes, however, this is not what you want.
For example, you may want to remove only intermediate generated files
(such as object files),
but leave the final targets
(the libraries)
untouched.
In such cases, you can use the NoClean method to prevent SCons
from removing a target during a clean: